CN102765198A - Vacuum assisted molding system of composite and molding method of composite - Google Patents

Abstract

The invention discloses a composite material vacuum auxiliary molding system, which comprises an open molding mould. The mold includes an upper mold and a lower mold. The upper mold is sealed and connected with a vacuum bag pressure system; the outer side of the mold is connected with a molding heating system. The invention also discloses a method for vacuum-assisted molding of composite material products: first prepare an open molding mold, place the prepreg on the lower mold, place the isolation film, release cloth, and air felt in sequence, and seal and connect Vacuum bag film, so that the formed vacuum bag pressure chamber is connected with the vacuum pump; the upper mold and the lower mold are connected to the molding heating system; under the condition of maintaining the vacuum bag pressure, the upper mold and the lower mold are closed, and the mold is passed through the molding heating system. Clamp and pressurize the prepreg, heat the upper and lower molds at the same time, and perform curing treatment after reaching the curing temperature. After the curing reaction is completed, the composite material product is formed. The process of the invention has low cost, strong versatility, less consumption of auxiliary materials, and can improve the use performance of products.

Description

Composite material vacuum assisted compression molding system and molding method

technical field

The invention belongs to the technical field of composite material forming technology, and in particular relates to a forming system and a forming method for improving the internal and surface quality of prepreg molded products.

Background technique

Vacuum-assisted compression molding system is a low-cost manufacturing technology that uses the combined action of vacuum negative pressure and molding pressure to prepare prepregs. Vacuumizing to form a negative pressure inside the molding system is a key factor to improve the internal quality of the product; applying external pressure is a key factor to increase the reinforcement content and resin density in the product. Therefore, the process of combining vacuum pumping and molding is an important technology to improve the performance of composite products.

The traditional vacuum bagging process using vacuum negative pressure to prepare and form can obtain composite products with better internal and apparent quality, but the resin content is relatively high and the mechanical properties are relatively low. The traditional molding process can obtain products with relatively good mechanical properties through pressurization, but the greater the molding pressure, the higher the risk of damage to the internal structure of the composite material; the lower the pressure, the more internal voids and defects. The traditional autoclave process can form products with good internal and external quality, but this method has high equipment costs and manufacturing costs, and the forming pressure is relatively low, resulting in high safety risks.

Aiming at the trachoma caused by air accumulation on the surface of SMC/BMC compression molding products, Chinese patent 200720187263.3 designed a vacuum-assisted molding mold for compression molding, which improved the surface defects of products and improved the surface accuracy of molding products. . However, this mold not only needs to design vacuum holes, but also needs to design high-precision sealing grooves to ensure the sealing effect after the mold is closed. The versatility of the mold is relatively low, and the process cost is relatively high.

Contents of the invention

In order to solve the problems existing in the prior art, the present invention proposes a composite material vacuum-assisted molding system with simple structure, convenient operation, low cost and high product quality, and also provides a low process cost, strong versatility, auxiliary A vacuum-assisted molding method for composite material products with less material consumption, low process threshold, good economy, and improved product performance.

In order to achieve the above object, the technical solution proposed by the present invention is a vacuum-assisted molding system for composite materials, the system includes an open forming mold, and the open forming mold includes an upper mold and a lower mold arranged oppositely, the lower mold The top of the mold is sealed and connected with a vacuum bag pressure system for applying vacuum bag pressure to the prepreg to be formed; the outside of the open molding mold is connected with a molding heating system for applying pressure to the mold.

In the above-mentioned molding system, both the upper mold and the lower mold are preferably single-sided molds, and the upper mold and the lower mold do not contact or close after mold closing.

In the above molding system, the length and width of the upper mold are preferably the same as the length and width of the product to be formed; each edge of the lower mold is preferably more than 30mm beyond each edge of the prepreg placed on it.

In the above-mentioned molding system, the vacuum bagging system preferably includes an isolation film, a release cloth and an air felt laid on the surface of the prepreg in sequence; the outer periphery of the air felt is connected with a vacuum bag film, and the vacuum bag film The outer periphery of the lower mold is coated on the upper surface of the lower mold through a sealed connection to form a vacuum bag pressure cavity, and the vacuum bag pressure cavity is connected to an external vacuum pump through a pre-embedded vacuum tube.

As a general technical idea, the present invention also provides a method for vacuum-assisted compression molding composite products based on the above system, including the following steps:

(1) Material preparation: Prepare an open molding mold including an upper mold and a lower mold according to the process parameters of the product to be molded, and place the prepreg for the molded product on the lower mold, and place the isolation film, demoulding Cloth and air felt are placed on the surface of the prepreg in sequence, and the vacuum bag film is sealed and connected to form a vacuum bag pressure cavity, so that the vacuum bag pressure cavity is connected with the external vacuum pump; the upper mold and the lower mold are respectively connected to the - molding heating system;

(2) Mold clamping and pressure: use the vacuum pump to clamp the upper mold and the lower mold under the condition of maintaining the vacuum bag pressure, and perform mold clamping mechanical processing on the prepreg through the mold pressing heating system. At the same time, the upper mold and the lower mold are heated by the molding heating system until the initial curing temperature of the post-curing cycle set for the prepreg is reached, and the curing process is carried out under the clamping pressure until the prepreg is cured After the reaction is finished, the temperature is lowered and the pressure is relieved to complete the molding of the composite material product.

In the above method, it is preferable to add a vacuum bag pressure step between the step (1) and the step (2). The specific operation method includes: turning on the vacuum pump to vacuum the vacuum bag pressure chamber to reach the set After the vacuum degree is reached, turn on the molding heating system to heat the lower mold until it reaches the initial curing temperature of the pre-curing cycle set for the prepreg, then start slow curing under vacuum bag pressure, and the curing treatment time does not exceed 6h. In the preferred vacuum bag pressure step, stepwise curing temperatures can be set in the pre-curing cycle, that is, curing is carried out by gradually heating up and keeping warm, but the highest curing temperature does not exceed the most intense temperature of the curing reaction of the raw material system. The range of the stepwise curing temperature is preferably 60°C to 120°C.

In the above method, during vacuuming, the air felt and the vacuum bag film can be adjusted so that the parts of the air felt and the vacuum bag film that are in contact with the upper simulation are flat and wrinkle-free.

In the above method, the stepwise curing temperature can also be set during the post-curing period. The temperature setting range is from the beginning of the reaction of the prepreg raw material system to the violent reaction and then to the post-curing stage. Gradual heating and heat preservation should be adopted. The multi-step method makes the material fully cured. At this time, the stepwise curing temperature in the post-curing cycle is preferably in the range of 60°C to 200°C.

In the above method, in the step of vacuum bag pressing and the step of clamping and pressurizing the mold, the vacuum degree when the vacuum tube is evacuated is preferably kept above -0.09Mpa.

In the above method, the working time of the vacuum bag press system, the clamping time of the open molding mold and the working time of the molding heating system can be optimized and determined according to the curing time of the prepreg. According to our repeated experiment results, the curing treatment time in the vacuum bag pressure is preferably 0.1-0.5 times of the curing treatment time in the mold clamping pressurization.

Compared with the prior art, the present invention has the advantages of: the composite material vacuum assisted compression molding system of the present invention has simple structure, convenient operation and low cost; the composite material products formed by using the vacuum assisted compression molding system and molding method of the present invention, Not only the quality is significantly improved, the internal defects of the product are less, and the performance is better; compared with the traditional autoclave process, the molding system and molding method of the present invention can greatly reduce equipment costs and manufacturing costs, and can obtain higher molding pressure , composite products with better mechanical properties can be prepared, and safety risks are reduced at the same time.

Description of drawings

Fig. 1 is a structural schematic diagram of a vacuum-assisted compression molding system for composite materials in the present invention.

illustration:

1. Upper mold; 2. Lower mold; 3. Upper hydraulic press; 4. Lower hydraulic press; 5. Prepreg; 6. Vacuum bag film; 7. Air felt; 8. Release cloth; 9. Isolation film; 10. Sealant; 11. Vacuum tube; 12. Vacuum bag pressure cavity.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Example:

A vacuum-assisted molding system for composite materials as shown in Figure 1, the system includes an open forming mold, the open forming mold includes an upper mold 1 and a lower mold 2 arranged oppositely, and a pair of treated molds is sealed and connected above the lower mold 2 The vacuum bag pressure system for forming prepreg 5 is implemented; the outer side of the open forming mold is connected with a mold pressing heating system (including hydraulic press upper 3 and hydraulic press lower 4 ). In this embodiment, the upper mold 1 and the lower mold 2 are single-sided molds, and the length and width of the upper mold 1 are the same as the length and width of the product to be formed; the edges of the lower mold 2 exceed the edges of the prepreg 5 placed on it The distance is more than 30mm. After the upper mold 1 and the lower mold 2 are closed, they do not touch or close.

The vacuum bagging system of the present embodiment includes an isolation film 9, a release cloth 8 and an air felt 7 sequentially laid on the surface of the prepreg 5; the periphery of the air felt 7 is connected to the vacuum bag film 6, and the periphery of the vacuum bag film 6 is sealed The glue 10 is coated on the upper surface of the lower mold 2 and forms a vacuum bag pressure chamber 12 , which is connected to an external vacuum pump through a pre-embedded vacuum pipe 11 .

A method for vacuum-assisted molding composite material products based on the above-mentioned vacuum-assisted molding system of this embodiment, the composite material product to be formed is a unidirectional carbon fiber reinforced epoxy resin composite material with a size of 250mm*250mm*2.5mm Flat plate, its specific molding process includes the following steps:

(1) Material preparation: Prepare raw materials according to the following specifications and requirements:

Reinforcement: T700SC carbon fiber;

Resin system: Epoxy resin TDE-85, anhydride THPA, accelerator DMP-30 prepared according to 100:100:0.9;

Prepreg: Carbon fiber and resin system are wound by winding machine;

Isolation film: high temperature resistant polyethylene film;

Release cloth: high temperature resistant white woven cloth;

Air felt: Polyester air felt with excellent air permeability and pressure resistance;

Vacuum bag film: nylon film with excellent temperature resistance;

Exhaust channel: 60-mesh woven mesh cloth is used;

Sealant: high temperature resistant pressure sensitive sealing tape.

(2) Material placement: As shown in Figure 1, cut 5 and six pieces of prepregs with a size of 250mm×250mm, and lay them on the upper surface of the lower mold 2 at 0°; prepare two pieces of 9 isolation films with a size of 250mm×250mm, and lay On the surface of prepreg 5; 8 pieces of 280mm×280mm release cloth, laid on the isolation film 9; 7 pieces of 280mm×360mm air felt, laid on the release cloth 8; 6 pieces of 400mm×450mm vacuum bag film, breathable A vacuum bag film 6 is connected above the periphery of the felt 7, and the periphery of the vacuum bag film 6 is coated on the upper surface of the lower mold 2 by a sealant 10 to form a vacuum bag pressure chamber 12, which is connected by a pre-embedded vacuum tube 11 and External vacuum pump connection.

(3) Vacuum bag pressure: Turn on the vacuum pump to evacuate the pressure chamber 12 of the vacuum bag, adjust the air felt 7 and the vacuum bag film 6 during vacuuming, so that the part of the air felt 7 and the vacuum bag film 6 in contact with the upper mold 1 is flat No wrinkles; when the vacuum degree reaches the set value above -0.09MPa, turn on the molding heating system to heat the lower mold 2 until it reaches the initial curing temperature of 85°C in the pre-curing cycle set for the prepreg, and then start a separate vacuum bag Slow curing treatment by pressing, the treatment time is 1 hour.

(4) Mold clamping and pressurization: After the above step (3) is completed, use the hydraulic press upper 3 and hydraulic press lower 4 of the molding heating system to clamp the upper mold 1 and the lower mold 2, while maintaining the vacuum bag pressure (-0.09MPa) Under certain conditions, the prepreg is mechanically pressurized to 0.5MPa through the molding heating system, and continues to cure for 3 hours at this temperature (85°C) and pressure, and continues to maintain vacuum (-0.09MPa) and external pressure (0.5 MPa), then the upper mold 1 and the lower mold 2 are heated and heated by the molding heating system at a heating rate of 3°C/min until the initial curing temperature of 120°C in the post-curing cycle set for prepreg 5 is reached, continue Carry out curing treatment under mold clamping pressure (vacuum negative pressure -0.09MPa, molding pressure 0.5MPa, 120°C), holding time is 4h, and finally keep the pressure until the molding system is naturally cooled to room temperature, and the pressure is released to complete the composite product. forming.

After inspection, the unidirectional carbon fiber-reinforced epoxy resin composite plate prepared in this example has a fiber volume content of more than 70%, a porosity of less than 0.5%, uniform thickness, and good appearance quality.

Claims (10)

1. composite vacuum aided compression molding system; It is characterized in that: said formation system comprises an open mould; This open mould comprises the upper die and lower die that are oppositely arranged, and said counterdie top is sealedly connected with a pair of prepreg to be formed and implements the vacuum bag pressing system that vacuum bag is pressed; The outside of said open mould is connected with the mold pressing heating system that mould is exerted pressure.

2. formation system according to claim 1 is characterized in that: said upper die and lower die are one-side mould, do not contact behind the said upper die and lower die matched moulds, not closed.

3. formation system according to claim 2 is characterized in that: the length and width of said patrix is identical with the length and width of intending moulded products; Each edge of said counterdie surpass its said prepreg of going up placement each more than the Edge Distance 30mm.

4. according to each described formation system in the claim 1～3, it is characterized in that: said vacuum bag pressing system comprises that lay is in barrier film, release cloth and the airfelt on said prepreg surface successively; The peripheral vacuum bag film that connects of said airfelt, the periphery of said vacuum bag film are coated on the upper surface of counterdie and form a vacuum bag through the mode of being tightly connected presses the chamber, and said vacuum bag presses the chamber to be connected through the vavuum pump of pre-buried vacuum tube with the outside.

5. method like arbitrary said formation system vacuum aided compression molding composite product in the claim 1～4 may further comprise the steps:

(1) the material tool is prepared: the open mould that comprises upper die and lower die according to the technological parameter preparation one of intending moulded products; And the prepreg that will be used for moulded products places counterdie; Barrier film, release cloth, airfelt are laid in said prepreg surface successively; The vacuum bag film that is tightly connected forms a vacuum bag and presses the chamber, makes vacuum bag press the chamber to be connected with outside vavuum pump; Described upper die and lower die are connected to a mold pressing heating system respectively;

(2) matched moulds pressurization: utilize said vavuum pump under the condition that keeps vacuum bag to press; Said upper die and lower die are carried out matched moulds; Through said mold pressing heating system said prepreg is carried out the pressurization of matched moulds machinery, through the mold pressing heating system upper die and lower die are heated simultaneously, until the initial solidification temperature of the back cure cycle that is reached for said prepreg setting; Carry out matched moulds and add the cured of depressing; Finish until the prepreg curing reaction, the moulding of composite product is accomplished in cooling, release at last.

6. method according to claim 5; It is characterized in that; Between said step (1) and step (2), increase a vacuum bag and press step, its concrete operation method comprises: open said vavuum pump and press the chamber to vacuumize to vacuum bag, after vacuum bag is pressed and reached the vacuum of setting; Open said mold pressing heating system heating counterdie; After the initial solidification temperature of the preceding cure cycle that is reached for said prepreg setting, begin to carry out the slow curing that independent vacuum bag is depressed, the cured time is no more than 6h.

7. method according to claim 6; It is characterized in that; Set the staged solidification temperature before described in the cure cycle; Promptly adopt the method that progressively heats up and be incubated to be cured, but the highest solidification temperature is no more than the most violent temperature of curing reaction of said prepreg raw material system, the scope of said staged solidification temperature is 60 ℃～120 ℃.

8. method according to claim 6 is characterized in that: the cured time during said vacuum bag is pressed is 0.1～0.5 times of cured time in the said matched moulds pressurization.

9. according to each described method in the claim 5～8; It is characterized in that: set the staged solidification temperature in the cure cycle of described back; Promptly adopt the method that progressively heats up and be incubated to be cured, the scope of staged solidification temperature is 60 ℃～200 ℃ in the cure cycle of said back.

10. according to each described method in the claim 5～8, it is characterized in that: the vacuum when said vacuum bag is pressed remains on-more than the 0.09Mpa.

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